Method and apparatus for integrating chemical and environmental sensors into an air purification filter through a reusable sensor port

ABSTRACT

A sensor device is disclosed for providing end of service life indication for an air purification filter. The sensor device has a cylindrical housing for insertion into a sorbent bed of a filter, and can be removed from the bed and reused at the end of the filter service. One or more sensors inside the housing are configured to sense physical/chemical characteristics of air passing through the sorbent bed, and to provide associated data to a sensor conditioning board within the housing. The sensor conditioning board processes the received data and conditions the data as desired. The housing is receivable in a cavity formed in the filter bed. A receiving structure receives the housing therein. Data from the one or more sensors can be used to calculate predicted end of service life of the filter. Other embodiments are described and claimed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US2011/046199 filed Aug. 2, 2011, which claims the benefit ofU.S. Provisional Patent Application No. 61/434,755, filed Jan. 20, 2011,and U.S. Provisional Patent Application No. 61/371,427, filed Aug. 6,2010, all of which are incorporated herein by reference in theirentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a method of integrating chemical andenvironmental sensors into an air purifying filter as anEnd-of-Service-Life-Indicator (referred to as ESLI hereafter) and/orResidual-Life-Indicator (referred to as RLI hereafter), and moreparticularly to a sensor post structure for hosting a plurality ofsensors that provide residual life indication and end of service lifeindication for an air purifying cartridge.

BACKGROUND OF THE DISCLOSURE

Air purifying filters typically do not have an unlimited service life.End users of air purifying devices must manage cartridge change-outusing objective information, data, or an end of service life indicator(ESLI). ESLIs can provide important safety information to users of anair purifying apparatuses, particularly where the purifying device isbeing used to remove toxic gases from the air being breathed. Commonlyused approaches to ESLI include passive and active solutions. Activesolutions often involve the use of electronic chemical sensors that areintegrated into the sorbent bed of the filter. Placing chemical sensorswithin the sorbent bed is problematic, however, because the sensors canundesirably disturb air flow in the filter. As a result, the sensor maynot detect actual impurity concentration for a majority of the airstream, which can result in false signals. In addition, the presence ofthe sensor inside the adsorbent bed may adversely affect the airpurification outcome and results in shorter service life time of thefilter cartridge.

Furthermore, an embedded sensor approach requires that the sensor bedisposed along with the cartridge when the service life of the cartridgeends, which greatly increases costs. Embedding a sensor in the sorbentbed also can increase the chance of improper bed packing. Further, itmay be technically challenging to mount multiple sensors at various bedlocations.

Accordingly, there is a need for an improved sorbent bed-embedded sensordesign for use in air purifying filter apparatuses.

SUMMARY OF THE DISCLOSURE

A device and method are disclosed for embedding a chemical sensor insidethe sorbent bed of a filter to provide information on the condition andusefulness of a filter used in a toxic environment. The design includesa device and method for either disposable or non-disposable chemicalsensors to provide enhanced reliability sensor technology.

A sensor device is disclosed for filter end of service life indication.The design may include a sensor post housing for insertion into asorbent bed of a filter cartridge. A chemical sensor may be disposedinside the sensor post housing. A sensor conditioning board, powered bya power supply, may be provided for conditioning and controlling thesensor and processing sensor data associated with the sensor posthousing. The sensor post housing may be positioned within a cavityformed in the filter bed. In one embodiment, the sensor device includesa receiving structure that is placed in the filter bed cavity forinserting the sensor post housing therein. The sensor device isparticularly useful as a proactive ESLI.

A method is disclosed for monitoring the end of service life of a filterusing the above described sensor device. In one embodiment, the methodincludes attaching the sensor post housing to an inhalation valvesupport of a respirator or blower, and inserting the sensor post housinginto a receiving structure to attach the filter to a mask. This canallow the opening of the sensor to align with the opening of the sensorpost housing.

The disclosed method and device can be particularly useful as aproactive ESLI for an air purification filter. The benefits of providingsuch a proactive end of service life indicator are that residual lifeindication (i.e., time remaining to breakthrough) can be provided muchearlier than the actual contaminant breakthrough time. This can providea user with a much bigger safety margin to wrap up work tasks safelyprior to requiring evacuation of a contaminated area.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, a specific embodiment of the disclosed device willnow be described, with reference to the accompanying drawings, in which:

FIG. 1A is a side view of an exemplary embodiment of the disclosedsensor post;

FIG. 1B is a top plan view of the sensor post of FIG. 1A;

FIG. 2 is cross-section view of the sensor post taken alone line 2-2;

FIG. 3 is a cross sectional view of a filter containing the sensor postof FIG. 1A therein;

FIG. 4 is a side cutaway view of the sensor post of FIG. 1A insertedinto a host cartridge attached to a mask body;

FIG. 5 is an isometric view of an inside portion of an empty filtercartridge showing a receiving structure for receiving the sensor post ofFIG. 1A;

FIG. 6 is an exploded isometric view of the sensor post of FIG. 1A;

FIG. 7 is an alternative embodiment of the sensor post of FIG. 1A;

FIG. 8 is a graph of experimental data representative of sensor postperformance as an End-of-Service Life Indicator (ESLI) for a hydrogensulfide filter cartridge; and

FIG. 9 is a graph of sensor-detected concentration over time, includingESLI prediction at various clock times and measured breakthrough.

DETAILED DESCRIPTION OF THE INVENTION

A device and method are disclosed for providing reusable sensors withina sorbent bed of an air purifying cartridge. Referring to FIG. 1A, thedevice may be a sensor device, or post, 10 having a hollow cylindricalsensor post housing 14 that supports a plurality of different types ofsensors 20 that may be mounted at a variety of positions along thehousing 14. In one embodiment, the housing 14 can be mounted to a filtercartridge 60 (FIG. 4) at a lower portion 12 of the housing 14 prior toengagement of the filter cartridge 60 onto a respirator 100. Inalternative embodiments, the sensor post housing 14 or sensor 20includes a mechanical connection for attachment to an inhalation valvesupport of the respirator 100. Alternatively, the sensor post 10 may befixed to the filter cartridge 60. Desirably, the sensor post 10 may bepositioned within the filter cartridge 60 so that the sensors 20disposed in or on the sensor post 10 can sense conditions in the sorbentbed 62 of the filter and can provide information to a processing devicethat can use the sensed information to estimate the residual servicelife time of the filter cartridge.

The sensor post 10 may be received within a cavity formed in theadsorbent bed 62 of a filter cartridge 60 when the cartridge is mountedinto the cartridge host 100. With proper mounting of the cartridge, eachof the sensor elements 20 on the sensor post 10 is positioned within thebed or adjacent to the bed, thus enabling the sensor elements 20 todetect key operational information regarding the air passingtherethrough. Examples of such operational information includecontaminant concentration(s) 22, air humidity 26, air temperature 24 andair flow rate 28 at different bed locations. A non-limiting, exemplarylisting of gases for which concentration information may be importantinclude formaldehyde, cyclohexane, ammonia, hydrogen sulfide, sulfurdioxide, chlorine, hydrogen chloride and hydrogen cyanide. Informationprovided by the sensors 20 can be used to provide the user with residuallife time and end of service life warnings.

As noted, the sensor post 10 can be mounted onto a cartridge host 100(e.g., a mask, a powered air purifying respirator (PAPR), a cartridgeadaptor). In addition, a plurality of sensors 20 can be mounted atdifferent locations on or in the sensor post 10. In one embodiment, thesensor post 10 is inserted into a filter cartridge 60 having a hostsensor receptacle, which in one embodiment includes a receivingstructure 50, as shown in FIG. 5. It will be appreciated that thedescribed arrangement enables the sensor post 10 to be reused when thecartridge 60 reaches its service life and is discarded. Thus, thecartridge 60 can be disassembled and the sensor post 10 removed prior todiscarding the cartridge.

In addition to being insertable/removable in the manner previouslyspecified, the sensor post 10 serves to position the one or more sensors20 at a variety of desired locations within the sorbent bed 62, thusproviding a wider range of information for the calculation of residuallife time and end of service life indicator as compared to priorembedded designs. As will be described in greater detail later, thesensor post 10 may also function as a mounting guide to facilitateproper mounting of a cartridge onto a respirator or other host 100(e.g., mask, cartridge adaptor, or powered air purifying respirators).

As seen in FIGS. 1A, 1B, 2, 4 and 6, the sensor post 10 may include ahousing 14, which in the illustrated embodiment is a hollow cylindricaltube. The sensor post 10 may have a plurality of sensors 20 mounted onor in the housing 14 at a variety of locations along the length of thehousing. A non-limiting exemplary listing of such sensors 20 includes ahumidity sensor 26, a temperature sensor 24, a flowrate sensor 28, aswell as an array of chemical sensors 22. Other types of sensors can alsobe used, as will be appreciated by one of skill in the art.

In one exemplary embodiment, the sensor post 10 has three chemicalsensors 22 a, 22 b, 22 c mounted at spaced apart locations along a sidewall of the housing 14. In addition, a humidity sensor 26 and atemperature sensor 24 are mounted on a top portion 13 of the post 10(FIG. 1B), while a flowrate sensor 28 is mounted on the lower portion 12of the post 10. The sensors 20 may be contained within, and protectedby, the sensor post housing 14. Thus, while the sensors 20 themselvesmay access the environmental and/or toxic conditions outside of thesensor post housing 14 through discrete openings 16 in housing 14, theinterior portions of the sensor post 10 are protected from suchexposure. The chemical sensors 22 may be isolated from each other by aplurality of sensor seals 30. These seals 30 may comprise appropriateseal members or vapor dams effective to prevent the contaminants frombypassing the sorbent bed 62 along the sensor post wall 14, and toisolate the conditioning board 40 (FIG. 2) and other sensors fromchemical contaminants that may corrode the board/sensors and/oradversely affect their operation. In one embodiment, the seals 30comprise elastomeric o-rings.

Referring to FIG. 2, a sensor signal conditioning board 40 may bepositioned within the housing 14 to function as a sensor conditioner,sensor controller, sensor signal pre-conditioner for the chemical,humidity, temperature, and flowrate sensors 20 In one embodiment, thesignal conditioning board 40 is a printed circuit board. The sensorcondition board 40 may control operation of the sensors 20 and mayprocess data received from the sensors 20. For example, and withoutlimitation, the signal conditioning board 40 may control the sensors,may process sensor signals, may execute instructions for calculatingresidual service life of the associated filter, and may produce signalsrepresentative of an end-of-service-life condition of the filter. Apower supply 45, either battery or externally provided, may be providedwithin the housing to power the sensor conditioning board 40.

The signal conditioning board 40 may include one or more microprocessorunits 140. Each microprocessor unit may include a microprocessor 142 andassociated memory 144. The memory may be volatile, non-volatile, or acombination of both.

In addition, the conditioning board 40 may include any of a variety ofanalogue signal amplifier and signal filter, digital signal processors,and/or other signal conditioning elements to provide a desiredpre-conditioned signal to a monitoring station. In one embodiment, thesepre-conditioned signals may be transmitted to a mother unit whichcontains the proper service life calculation algorithm and which isresponsible for providing proper RLI/ESLI warning information to theuser. In another embodiment, these signals are read by a localmicrocomputer or microcontroller unit which is equipped with the properRLI/ESLI calculation algorithm and which can give out proper RLI/ESLIwarnings to the user. The RLI/ESLI calculation algorithm may utilize theproper breakthrough models, such as the one developed by Ding et al, tomodel the evolution of the contaminant concentration profiles inside thebed, and hence calculate the residual life time of the filter cartridgebased on the modeling of the evolution process of the contaminantconcentration profiles. This process is different from traditionalRLI/ESLI calculation method in that it utilizes relevant adsorptionprocess modeling to predict the RLI/ESLI before any breakthrough eventhappens. As a result, this method can give out proactive RLI/ESLIinformation much earlier than the actual breakthrough event, thus givingthe user much more time to take according action to avoid potentialhealth damage.

In one embodiment, the host filter or host mask unit 100 comprise themonitoring station and may include a hard-wired or wireless receiver andwarning information or alarm that can be tripped when an end-of-lifecondition is approaching. The warning information may take the form ofany visual, audio, or mechanical signals that can be noticed andunderstood by the user. Such warning information may be generated by anelectronic unit either mounted on the sensor post body 10 itself, or ona sensor post host unit such as a mask or a PAPR

Pre-conditioned signals and/or post conditioned warning signals may takethe form of either digital or analog signals or both, and may betransmitted from the sensor post 10 to the host filter/mask via acommunication port 42. The communication port 42 may be a hard-wired orwireless communication port for providing a variety of data from (orabout) sensor devices 20 to the host filter or host mask unit 100. Thus,in one embodiment, the communication port 42 includes a hard wiredconnection 41. Alternatively, the communication port may include awireless transmitter 43 to wirelessly transmit pre-conditioned signalsto the host filter/mask 100. Alternatively, or in addition, theconditioned signals may be transmitted (via hard wire or wirelessly) toa separate alarm or monitoring station that is separate from the hostfilter or host mask unit 100.

The wired or wireless communication port 42 may provide data exchangebetween the sensor post 10 and any monitoring mother unit mounted on thehost filter/mask 100 or other physical units. The warning signals,transmitted via a proper unit and taken any visual, audio, or mechanicalform, may convey the information of any of, but not limited to, thefollowing: host filter type, host filter part number, host filter serialnumber, date of manufacturing, date of expiration, previous usage,residual life time, predicted end of service life time, environmentalconditions, critical filter cartridge change out signal, criticalimmediate evacuation signal, etc.

To protect the inner components, including the signal conditioning board40, from the gases that may be present within the filter 60 duringoperation, the sensor post 10 may include a an end seal 44 to seal theinterior of the sensor post housing 14 from the environment. In oneembodiment, the seal 44 may be an epoxy seal. Alternatively, the seal 44may be an appropriate gasket or o-ring connection.

As previously noted, the communication port 42 may provide hard-wired orwireless digital communication signals to and from the sensor post 10.Digital communication signals may include, without limitation, modelparameters, residual life time data, and end of service life timewarning data. The signal conditioning board 40 may include one or morenon-volatile data storage memory units 144 to store this and otherinformation, some or all of which may be modified via the one or moreassociated microprocessors 142.

Referring to FIG. 3, a cross sectional view of a filter 60 is shown. Thefilter 60 may include receiving structure 50 (FIG. 5) for holding thesensor post 10 in a desired position with respect to an adjacent sorbentbed 62. The receiving structure 50 may, in one embodiment, form acylindrical cavity within the sorbent bed 62 and may have one or moresensor orifices 18 disposed in a side wall 70, and/or on a top surface72. Theses orifices 18 may be positioned directly adjacent the sensors20 of the sensor post 10 when the post is positioned within thereceiving structure 50. The orifices 18 may permit chemical vaporingress into the cavity so that the chemical vapors can contact thesensors 20 of the sensor post.

In an alternative embodiment, the sensor post 10 may form a cavity inthe sorbent bed 62 upon its insertion therein, without the use of areceiving structure. In this embodiment, the sensor post 10 may form acomponent part of the filter 60. In another alternative embodiment, acavity may be pre-formed within the sorbent bed 62 of the filter 60. Insome embodiments, the sensor post 10 will be attached to a host 100(e.g., a mask, an adaptor, or a PAPR unit), and then the combinationwill be engaged with a filter cartridge 60. When a cartridge 60 ismounted onto a host 100 equipped with a sensor post 10, the sensor post10 is inserted into the sensor post cavity of the cartridge. Where thefilter cartridge 60 includes a receiving structure 50 and the cartridgeis properly mounted to the host 100, the top 13 of the sensor post 10will align with top surface 72 of the mounting structure and each of theside sensor orifices 18 will be positioned adjacent respective sensors20 and will be sealed from each other by adjacent sensor seals 30.

As an alien object intruded into the sorbent bed, the receivingstructure 50 may result in certain interference to the air flow patterninside the sorbent bed and have negative effect on the filterperformance. For example, a small fraction of the air flow may creepthrough the bed along the wall of 50 without fully contacted with theadsorbent material. To prevent this from happening, the receivingstructure 50 may be baffled around the contacting surface to block theair flow along the surface of 50. As seen in FIG. 5, which illustratesthe interior of an empty filter cartridge in which receiving structure50 is integrated into the cartridge, a plurality of baffling elements 52surround the receiving structure 50 to prevent vapor passage through thebaffled area.

As shown in FIG. 3, the top surface 72 of the receiving structure 50 canbe a screen, or a protective membrane, to protect the top 13 of theinserted sensor post 10 from particulate or liquid contaminants whilestill allowing vapor to permeate the screen/membrane to contact thesensors 24, 26 disposed at the top of the sensor post 10. In oneembodiment, the filter cartridge 60 includes a breakable protective sealelement on the opening of the receiving structure 50 to seal the insideof the receiving structure from the outside environment prior toinsertion of the sensor post 10. The seal element may be broken by thetop 13 of the sensor post 10 when the post is inserted into thereceiving structure. This seal allows the filter cartridges that havethe sensor post receiving cavity built inside be used on normal airpurification respirators on which no sensor post element is installed.

In operation, the signal conditioning board 40 may receive a pluralityof signals from the various sensors disposed on the sensor post 10.Thus, the humidity 26 and temperature 24 sensors on the top of thesensor post 10 may provide humidity and temperature signals, while afirst chemical sensor 22 a may provide site concentration signals at atop portion of the sorbent bed 62. Additional chemical sensors 22 b, 22c may provide signals regarding chemical vapor concentration atdifferent sorbent bed levels. Flowrate sensor 28, which may be mountedon a side wall of the sensor post housing 14 adjacent the outlet of thecartridge 60 may provide flowrate signals representative of the rate ofair being drawn into the mask 100 or other host structure.

The conditioning board 40 can receive each of these signals and convertthem into a desired form (e.g., analog voltage, analog current, digital,digital wireless, or other like transmitting form). One or more of thesesignals may be processed by the one or more microprocessor units 140associated with the signal conditioning board 40 prior to transmissionto the host filter 60 or other receiver via the communications port 42.

Referring now to FIG. 4, sensor post 10 is shown engaged with a hostfilter cartridge 60 and a mask body 100. As can be seen, a lower portion12 of the sensor post 10 engages a portion of the mask body 100 while atop portion 13 of the post is received within the filter cartridge 60.Thus arranged, as the cartridge 60 is mounted onto the host 100, thesensor post 10 can serve as a mounting guide to facilitate the propermounting of the cartridge 60 on the host 100. In one embodiment, thesensor post 10 may be initially mounted in the filter cartridge 60 andmay be inserted into the mask body 100 as the cartridge is mounted tothe mask body 100. In another embodiment, the sensor post 10 may beinitially mounted in the mask body 100 and may be inserted into thefilter cartridge 60 as the cartridge is mounted to the mask body 100.

The sensor post 10 may have one or more chemical sensors, shown as 22a-c as an example embodiment, mounted along the length of the housing14, pair one or more of humidity and temperature sensors 24, 26 mountedon the top portion 13 of the housing 14, and a flowrate sensor 28mounted adjacent the lower portion 12 of the housing. Each of thechemical sensor 22 a-c may be isolated from the others via a pair ofadjacent sensor seals 30. Internal to the sensor post 10 may be a signalconditioning board 40 that functions as a signal pre-conditioner for thechemical, humidity, temperature, and flowrate sensors. Pre-conditionedsignals may be transmitted from the sensor post 10 via a hard wired orwireless connection in the manner previously described. The internalvolume of the sensor post 10, including the signal conditioning board40) may be sealed from the surrounding environment by an end cap 44 (seeFIG. 6) sealed to the housing 14 using epoxy, or a gasket or o-ringconnection.

In one embodiment, the host 100 (e.g., a mask, an adaptor, or a PAPRunit) is equipped with a sensor post 10, and a filter cartridge 60 isprovided separately. Thus, when the cartridge 60 is mounted onto thehost 100, the sensor post 10 is aligned with the receiving structure 50of the cartridge 60 to guide the cartridge 60 down into engagement withthe host 100. Once the cartridge 60 is properly mounted to the host 100,the top of the sensor post 10 aligns with the top surface 72 of thereceiving structure 50. As previously noted, this top surface 72 can bea screen or membrane that allows the temperature and humidity sensors24, 26 to obtain relevant information regarding the filter duringoperation. In this position, each of the side sensor orifices 18 ispositioned centrally with respect to each of the plurality of chemicalsensors 22 a-22 c, and sealed from adjacent chemical sensors via a pairof associated sensor seals 30.

In one embodiment, the invention includes the sensor device 10 for endof service life indication having the sensor post housing 14 forinsertion directly into the sorbent bed 62 of the filter cartridge 60.The housing 14 may be formed to fit within a cavity that has been formedwithin the sorbent bed 62. The cavity may be pre-formed in the bed priorto insertion of the sensor post housing 14. Alternatively, the cavitymay be formed in the bed through the process of inserting the housing 14in the sorbent bed 62.

In additional embodiments, the housing 14 alone may be provided as apart of the filter cartridge 60, positioned within a cavity in thesorbent bed 62. The internal components of the sensor post 10 may thenbe inserted into the housing 14 to position the sensors 20 at desiredpositions within the sorbent bed 62.

As previously noted, the chemical sensors 22 a-22 c are sealed off fromeach other via seals 30, which results in individual vapor “chambers”associated with each sensor, and each of the sensors 22 a-22 c hasaccess to the vapor space within the filter 60 via an associated orifice18 (see FIG. 3) The individual vapor chambers may be formed by the outersurface of the housing 14, an inner surface region of the receivingstructure 50 of the filter cartridge 60, and a pair of seals 30.Alternatively, the chemical sensors 22 a-22 c may share a common vaporspace, allowing a conduit for effective vapor flow therebetween.

In some embodiments, the orifices 18 are positioned such that themaximum concentration level that the chemical sensors are exposed willnot be reached at the end of the service life time, in order to protectthe chemical sensor from exposing to too high chemical concentrationlevels to avoid or minimize saturation with contaminant from theenvironment.

FIG. 7 shows an alternative embodiment of a sensor post 150 having anexterior configuration that differs from that of sensor post 100 of FIG.1A. The sensor post 150 of this embodiment may have any and/or all ofthe functional features of the sensor post 10 described in relation toFIGS. 1-6. For example, the sensor post 150 may include openings 116 inthe housing 114 to enable the sensors disposed within the housing toaccess the environmental and/or toxic conditions outside of the sensorpost housing 114. In contrast to the embodiment of FIG. 1A, the openings116 of sensor post 150 are positioned at or near the distal end 152 ofthe sensor post 150. The distal end 152 will be that portion of thesensor post 150 that is positioned within the filter cartridge 60 (seeFIG. 4) in use.

The sensor post 150 may also include a communication port 154 disposedat a proximal end 156 of the sensor post 150 to enable signals generatedby the sensors disposed in the housing 114 to be communicated to thehost filter or host mask unit 100 (see FIG. 4). In the illustratedembodiment this communication port 154 includes a hard wired portion158. As with the embodiment of FIG. 1A, the communication port 154 canbe hard wired or wireless connection.

Between the distal and proximal ends 152, 156, the housing 114 mayinclude a keyed external geometry 158 for engaging a portion of the maskbody 100 to position the distal end 152 of the post within the filtercartridge 60.

As noted, the sensor post 150 of FIG. 7 may include any or all of thefeatures of the sensor post 10 described in relation to FIGS. 1-6. TheFIG. 7 embodiment illustrates that the external configuration of thesensor post can take any of a variety of desired external forms.

FIG. 8 is a graph illustrating exemplary experimental datarepresentative of sensor post performance as an End-of-Service LifeIndicator (ESLI) for a hydrogen sulfide filter cartridge. The graph isan illustration of hydrogen sulfide gas concentration (in parts permillion) vs. time (in minutes), and shows the efficacy of the sensorpost in detecting hydrogen sulfide gas prior to filter breakthrough. Thesensor detects the presence of chemical prior to a chemical sensorplaced at the outlet of the filter. As can be seen, the permissibleexposure limit (PEL) for hydrogen sulfide, 10 ppm, is detected at 26.2minutes which is 137 minutes prior to the time the chemical “breaksthrough” the filter at this concentration.

Table 1 below shows exemplary laboratory data demonstrating that thesensor post is capable of detecting particular chemicals prior to filterbreakthrough, and that filter breakthrough with the sensor post does notdegrade more than 11% overall for the chemicals presented. The averagebreakthrough time of all five experiments is 95.5 minutes without thesensor post, labeled “baseline”. The average breakthrough time of allfive experiments is 84.8 minutes with the sensor post, labeled “filteroutlet”. The degradation is less than or equal to 11% as measured bythese tests.

TABLE 1 RH Conc. tb, tb, tb, Chem (%) (ppm) sensor post filter outletbaseline C6H12 50 1000 10.0 47.8 65.0 80 1000 3.0 40.2 48.2 H25 50 100026.2 163.3 186.8 NH3 50 1000 5.9 48.2 47.6 50  300 26.8 124.7 130.0

Data shown in Table 2 below demonstrate the effectiveness of the sensorpost when coupled with an ESLI estimation calculation and the impact ofsensor location on prediction accuracy with time. Due to regulatorystandards the estimated ESLI should be no more than 90% of the measuredESLI. In all cases presented below, this is the case. ESLI estimationincreases with time and is dependent on sensor location. FIG. 9 plotsthe sensor detected concentration over time, including ESLI predictionat various clock times and measured breakthrough.

TABLE 2 Flow, Chemical RH, % l/min Location Parameter Time (min) Ammonia50 64 ½ of sorbent bed Clock Time 20 30 40 50 depth (min) Estimated ESLI74 58 58 58 (min) Measured ESLI 62 (min) H₂S 50 64 ½ of sorbent bedClock Time 20 25 30 35 40 depth (min) Estimated ESLI 28 36 41 42 42(min) Measured ESLI 46 (min) H₂S 25 64 ½ of sorbent bed Clock Time 20 2530 35 40 depth (min) Estimated ESLI 28 32 34 35 42 (min) Measured ESLI41 (min) H₂S 85 64 ½ of sorbent bed Clock Time 20 25 30 35 40 depth(min) Estimated ESLI 30 36 34 50 42 (min) Actual ESLI 47.5 (min) H₂S 5085 ½ of sorbent bed Clock Time 15 20 25 27 depth (min) Estimated ESLI 2429 35 37 (min) Measured ESLI 33 (min) H₂S 50 50 ⅓ of sorbent bed ClockTime 20 40 60 80 100 depth (min) Estimated ESLI 43 70 84 85 82 (min)Measured ESLI 121 (min)

The illustrated embodiments are described as utilizing a single sensorpost 10 with a single filter cartridge 60. It will be appreciated,however, that more than one sensor post 10 may be used with a singlefilter cartridge 60. In addition, although a sensor post 10 has beendescribed with a certain arrangement of sensors, it will be appreciatedthat a variety of different sensor types, configurations and numbers canbe used to provide a desired sensing platform. In addition, it is notcritical that all sensors provide data to the signal conditioning boardat the same rate, nor that all sensors in the sensor post be utilized atthe same time. Thus, it is contemplated that a single sensor post mayinclude a plurality of sensors, and that the programming of the signalconditioning board 40 may be such that only certain sensor signals areutilized for a particular filter cartridge application.

The illustrated embodiments are described as a cylindrical body that isinserted into a matching cylindrical hole. It will be appreciated,however, that the sensor device be made into any geometric shape, suchas a rectangular or square rod, a hexagonal rod, etc. so long as it canbe embedded into the bed and taken out freely without damage to thefilter body. Furthermore, depending on the geometry of the objectfilter, the sensor device may not need to be inserted into a receptaclehole; rather, it can be partially embedded into an receptacle space, oreven attached by the side of the filter, as long as the sensors beexposed to the media at a desired bed depth.

Some embodiments of the disclosed method and device may be implemented,for example, using a storage medium, a computer-readable medium or anarticle of manufacture which may store an instruction or a set ofinstructions that, if executed by a machine, may cause the machine toperform a method and/or operations in accordance with embodiments of thedisclosure. Such a machine may include, for example, any suitableprocessing platform, computing platform, computing device, processingdevice, computing system, processing system, computer, processor, or thelike, and may be implemented using any suitable combination of hardwareand/or software. The computer-readable medium or article may include,for example, any suitable type of memory unit, memory device, memoryarticle, memory medium, storage device, storage article, storage mediumand/or storage unit, for example, memory (including non-transitorymemory), removable or non-removable media, erasable or non-erasablemedia, writeable or re-writeable media, digital or analog media, harddisk, floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact DiskRecordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk,magnetic media, magneto-optical media, removable memory cards or disks,various types of Digital Versatile Disk (DVD), a tape, a cassette, orthe like. The instructions may include any suitable type of code, suchas source code, compiled code, interpreted code, executable code, staticcode, dynamic code, encrypted code, and the like, implemented using anysuitable high-level, low-level, object-oriented, visual, compiled and/orinterpreted programming language.

While certain embodiments of the disclosure have been described herein,it is not intended that the disclosure be limited thereto, as it isintended that the disclosure be as broad in scope as the art will allowand that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

What is claimed is:
 1. A sensor device for end of service lifeindication, comprising: a housing having an outer surface, alongitudinal cavity, and at least one opening along the outer surface; asensor for detection of one or more chemicals, the sensor positionedwithin the longitudinal cavity adjacent the at least one opening; asensor conditioning board for processing sensor data from the sensor;and a power supply for powering the sensor conditioning board, whereinthe housing is removably insertable into a cavity in a sorbent bed of afilter element.
 2. The sensor device of claim 1, further comprising: areceiving structure in the cavity in the sorbent bed, the receivingstructure receiving a portion of the housing therein, wherein thereceiving structure includes at least one opening extending from aninside of the receiving structure to an outside of the receivingstructure, the opening configured to allow vapor flow from said sorbentbed to the at least one opening of the housing when the housing isplaced within the receiving structure
 3. The sensor device of claim 1,wherein the receiving structure extends the length of the sorbent bed ofthe filter.
 4. The sensor device of claim 1, wherein the sensorcomprises one or more chemical concentration sensors positioned along alength of said housing, each of said sensors associated with an openingin said housing.
 5. The sensor device of claim 1, wherein the at leastone opening is located at a distal end of the housing away from a maskattachment point.
 6. The sensor device of claim 1, further comprising anenvironmental sensor package within the longitudinal cavity of thehousing having at least one sensor selected from the group consisting ofa chemical concentration sensor, a temperature sensor, a relativehumidity sensor, and a flow rate sensor.
 7. The sensor device of claim1, further comprising an external seal along the circumference of thesensor post housing, said external seal for sealing the outer surface ofthe housing to a receiving structure of the sorbent bed.
 8. The sensordevice of claim 1, wherein the sensor comprises a plurality of chemicalconcentration sensors positioned along a length of said housing, thedevice further comprising a plurality of internal seals, at least one ofsaid internal seals positioned adjacent the outer surface of the housingto isolate the chemical concentration sensors from each other.
 9. Thesensor device of claim 1, wherein the sensor conditioning board includesa processor and a memory, the processor configured to executeinstructions for determining a service life of said sorbent bed of saidfilter element.
 10. The sensor device of claim 1, further comprising areceiving structure in the cavity in the sorbent bed, the receivingstructure receiving a portion of the housing therein, the receivingstructure including a membrane at a top portion thereof for isolating anend of the housing from particulate or liquid contaminants in thesorbent bed, but allowing gas permeation.
 11. The sensor device of claim1, wherein the housing includes a mechanical connection for attachmentto an inhalation valve support of a support member of a respiratorsystem.
 12. The sensor device of claim 1, wherein the housing includes amechanical connection for attachment to an inhalation valve support of amask.
 13. The sensor device of claim 1, further comprising a vapor damfor isolating the conditioning board and sensors for chemicalcontaminants.
 14. The sensor device of claim 1, wherein the power sourceis selected from the group consisting of a battery and an external powersource.
 15. The sensor device of claim 3, wherein the receivingstructure surface proximate to the sorbent is baffled to preventchanneling of vapor contaminants.
 16. The sensor device of claim 1,wherein the sensor post housing extends from the front portion of filterbed so that the sensor port is position towards inlet of the sorbentbed.
 17. A predictive end of service life indicator comprising thesensor device of claim
 1. 18. A method for monitoring end of servicelife of a filter, comprising the steps of: providing the sensor deviceof claim 2, wherein the receiving structure is embedded into the sorbentbed of a filter; attaching the sensor post housing onto an inhalationvalve support of a support selected from the group consisting ofrespirator and blower; and, inserting the sensor post housing into thereceiving structure with attachment of the filter onto the mask, whereinthe at least one opening of the sensor aligns with the at least oneopening of the sensor post housing.
 19. A method for monitoring residuallife of a filter, comprising the steps of: providing the sensor deviceof claim 2, wherein the receiving structure is embedded into the sorbentbed of a filter; attaching the housing onto an inhalation valve supportof a support selected from the group consisting of respirator andblower; and, inserting the housing into the receiving structure whileattaching the filter onto the mask, wherein the at least one opening ofthe sensor aligns with the at least one opening of the housing; and,calculating service life based on a trend read-out determined using datareceived from said sensor.
 20. The method of claim 19, furthercomprising repeating the calculating step at set time intervals.
 21. Themethod of claim 19, further comprising an algorithm to calculate theresidual life of the said filter and predict the end of service lifetime of the said filter by modeling the collected chemical concentrationprofile into a predefined model, and use the model to predict theevolution progress of the concentration profile at any given time, thusproviding the residual life time as well as the end of service lifetime.
 22. The sensor device of claim 1, wherein information related toresidual life time, including but not limited to preconditioned sensorsignals and post-conditioned model signals, is transmitted out of thesensor post as an analog electric signal, as a digital electric signalof any form, a mechanical signal, a visual signal, or an audio signal.23. The sensor device of claim 1, wherein the outer surface of thehousing having a geometric shape in cross-section, the outer surfaceinserted at least partially within the cavity of the sorbent bed orattached to an edge of the sorbent bed to expose the sensors to gasmedia via the at least one opening.